Among the 10 incarnations of Vishnu, the Kurma avatar is also considered to be one of the most important avatars of Vishnu. Kurma is the tortoise incarnation of Lord Vishnu, who appeared to help the devas (gods) and asuras (demons) in the churning of the cosmic ocean of milk (Ksheera Sagara) to obtain the nectar of immortality.
In the story, Devas and Asuras were at war, and the Devas were losing. They sought help from Lord Brahma, who advised them to obtain the nectar of immortality from the cosmic ocean of milk(Ksheera Sagara). To do this, they needed a massive churning rod and a pivot, but nothing suitable was available. Lord Vishnu appeared as Kurma, the giant tortoise, and offered to serve as the pivot for the churning rod. The Devas and Asuras then churned the ocean using the serpent Vasuki as the churning rope. Many valuable items emerged from the ocean, including the goddess of wealth, Lakshmi, and the nectar of immortality.
In this avatar, Lord Vishnu is often depicted as holding up Mount Mandāra in the ocean, with the lower body of a tortoise and a human upper body with arms, holding a conch and a discus. The story of the Kurma avatar is believed to symbolize the power of determination and cooperation. It teaches that even the most difficult tasks can be accomplished with the help of others.